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Message board > Engines > Yamaha 80 tests

Message 12 of 12
Posted by member Andy Mcmullan on Friday 10 April 2009

Hi Steve I was just looking at an old post on proping a 70hp 4 stroke Suzuki. Seems that a 13 x 13 worked best. Interesting! http://www.hardy-owner.org.uk/forum/en1107792649.htm Cheers, Andy

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Message 11 of 12
Posted by member Damian on Tuesday 31 March 2009

I had a 40hp Merc fourstroke on my River Pilot and I can confirm 15 knots at WOT...going down the Strangford Narrows at springs on the ebb tide!

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Message 10 of 12
Posted by member Andy Mcmullan on Tuesday 24 March 2009

I was just reading a copy of a used test PBO did on a 1986 vintage Pilot in 1997. It had a 45hp Honda 4-stroke and according to the tester was planing at 15 knots and 5500 revs. In the article there were 2 adults on board. I don't know how they measured the speed but I suppose you'd know you were well on the plane at that speed. Just thought I'd pass that on as we're on the subject of performance and getting maximum revs out of the engine. Cheers Andy

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Message 9 of 12
Posted by member Roger Beese on Thursday 19 March 2009

Hi Thank you Micheal and Steve for your comments I will take you up on your offer Steve I have been on the Bay today Tried a 10 pitch and moved a small amount of gear foreward or off the boat achieved 10.5 knts (19/3/09) More items to take off and then try the 13 pitch again I am on 01633664656 perhaps we could meet up next week Steve

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Message 8 of 12
Posted by member Michael Herridge on Wednesday 18 March 2009

For what it's worth at a push we can get a tad over 17knts with a Suzuki DFV 50 in an old but lightly loaded Pilot. Flat calm. We have Doelfins but no tabs. This is at around 6000 rpm which I think is top whack. Noisy and expensive on petrol. I very much doubt that one could ever get any faster with a 50. Inshore a 50 is fine, offshore it gets a bit breathless. After using 50 for a few years I'd suggest that a modern, light 75/80 is what is really needed but with these older boats the engine starts to be worth more than the boat itself! Michael

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Message 7 of 12
Posted by member Steve Hook on Tuesday 17 March 2009

Roger. If you look at all the info above & elsewhere on the site youll see that 50 is not powerfull enough to get the pilot 20 on the Plane Im based at Penarth marina we spoke once before.....call me on 01568 760 677 if you want to discuss performance or meet me at Cardiff for a try on my boat now ive upgraded to 80hp.......Steve

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Message 6 of 12
Posted by member Roger Beese on Monday 16 March 2009

Hi All Just tried my HP20 with Honda 50 in Cardiff Bay Only 7Knts --- dissapointing What size prop should I try (pitch and diam) I am not looking for speed more for economy But I would like nearer 16 knts

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Message 5 of 12
Posted by member Steve Hook on Sunday 15 March 2009

Hi....just for correction made a slight error on the measurements i gave.....should read cav plate to transom bracket on engine 538mm this puts cav plate approx 1.5in below transom....Thanks Steve

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Message 4 of 12
Posted by member Steve Hook on Sunday 15 March 2009

Thanks for the info.....unfortunatly Andy..I was the installer but having read in he tech info that the transom height suitable for the yam 80 was 20in I mounted it straight onto the 20in measured transom of the Pilot.The mounting holes for the Yam are exactly the same as the 50hp Mariner I removed so no drilling required... only on the day befor launch a marine engineer told me that he was having to raise a new engine he installed on an 18ft Raider to achive more revs...I then looked at my boat & could not understand why the cavitation plate was lower that the hull...Measuring the engine i found that the cav was 608mm from the transom bracket ....approx 2in below the hull. called Yam tech & they suggested launch & try as in their view cav position varies from boat to boat ideally 50mm below the water when the boat is on the plane......Hav just just sourced a loan of a 15in prop so will try this next week.....My aim is not top speed but having purchased a nearly new(5Hrs) engine to get the set up right. thanks all for your input will keep you posted.

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Message 3 of 12
Posted by member Andy Mcmullan on Saturday 14 March 2009

Hi Steve I was wondering how you were getting on. Thanks for getting back. It seems surprising that you are only making 5K revs. Thats an interesting idea about raising the engine and I have read in the past that it is important to have the cav plate level with the lower part of the stern as you say. Even slightly higher on more performance oriented hulls. I just had a look at my boat in the garden and the motor is raised an inch or so above the transom edge. There is adjustment available by taking the top bolts out and relocating them in the other holes. The lower bolts also slide up and down in their channels. Obviously the boat needs lifted out as you say and fresh sealant applied. Thankfully no new holes would be needed. It's a pity the installer did not take account of this when fitting the outboard. Another thing I was thinking about the earlier hull is that people used to fit transom wedges between the outboard bracket and the hull. The reason for this from memory was that the transom was at more of an angle on this hull, that tended to make the outboard 'lean' back a bit too much. This might have directed thrust too far down? Not sure about this really but thought it was worth mentioning. There's more detail on wedges on the forum. You would think that power trim would negate this effect somewhat! I have the later Pilot hull with the more vertical transom and no keel. Dominic and Nicola Gribben have the same hull as you and extensive experience cruising with their 75hp Honda. Maybe they can offer some assistance? I think their motor revs out no problem. Propellers aren't cheap so you need to draw the line at some point. It's great that you have your boat on the water so early in the season and can enjoy the early spring weather. I will be taking my boat to get a new cover made in a few weeks so my launching is a long way off. Keep us posted on how you progress. Cheers Andy

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Message 2 of 12
Posted by member Dominic And Nicola Gribbin on Saturday 14 March 2009

Hi Yes, our Pilot's 75 cavitation plate is level with the semi displacement hull of our '93 hull. 15 inch prop. Stub keel exactly as Steve describes. Produces 5K plus RPM flat out but we get only 20 knots (maybe 21 ) when cruising in ideal condions with just two average weight passengers. With 3 growing boys & kit thats now history and I'm throttling back for a nice sedate life at 13 knots on the plane. Our Honda purrs at this speed and its a very civlised & effective touring speed. The key to our long distance cruising has been the addition of Lectro trim tabs and their fine tuning underway. Totally transforms the Pilot's sea keeping and stability at speed. Best Dominic and Nicola.

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Message 1 of 12
Posted by member Steve Hook on Thursday 5 March 2009

Message for Andy Mcmullan. Just relaunched "Johnnie Cake" 1994 Pilot 20 with Yam 4 stroke efi F80 & 17" prop as mentioned on the forum under "Engine Hardy 20"...nice flat day with little wind in Cardiff Bay (non tidal)lightly loaded & no passengers. could only archive max 5krpm which pushed the boat along at approx 25mph....trimming the engine in/out made neglige able difference & trim tabs although getting on plane quicker had little effect on speed/rpm...talked to Yam tech they suggest propping down to 15" (250rpm increase/1")Also been advised to raise engine up. Its hooked directly on the transom but this leaves the cavitation plate approx 2" below the hull.....It points out that getting this whole engine/prop/tabs setup right is not for the feint hearted.......Hull design plays a great part in this & you cant just assume that boats of the same year have the same hull shape. mine has the stubb keel that (from memory ends approx 2ft from the transom & portrudes down approx 10". so for anyone out there asking what engin/prop/performance etc make sure you check like for like......As for now I,ll just enjoy the boating for a while before considering the lift out/in costs to do any more changes Happy days Steve

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